We have not yet received IRB approval to start recruiting patients. The plan is to recruit the following patient groups: 1. Group A: 15 patients with HIV infection from Dr Avi Naths All Hands screening cohort. 2. Group B: 15 subjects without HIV infection from Dr Avi Naths All Hands screening cohort AND with one or more of the following: a.Hypertension, as defined by treatment with medications for hypertension or with a systolic blood pressure at screening 140mm Hg. b.Diabetes, as defined by history or by HbA1C 6.5%. c.Hepatitis C infection as documented by history, or with screening lab results of a positive Hepatitis C antibody or a detectable Hepatitis C viral load. d.A positive response to the screening questions, Have you ever used cocaine? Heroin? or Amphetamines? e. A positive response to the screening Client Diagnostic Questionnaire, Has alcohol ever affected your work or home life? 3. Group C: 15 patients without HIV infection from Dr Avi Naths All Hands screening cohort AND without any of the conditions listed for Group B. Data acquisition procedures and image data processing: after the subjects are found to satisfy the inclusion and exclusion criteria and after informed conset is obtained, they will be referred for a one-time only 18F-FDOPA PET scan. Upon presentation to the PET department at the NIH Clinical Center, each subject will receive 200 mg of carbidopa (to reduce peripheral metabolism of FDOPA and increase tracer availability in the brain) one hour prior to the injection of labeled FDOPA. After one hour, subjects will be positioned in the CPS/CTI High Resolution Research Tomograph (HRRT), head-only camera and a swimming cap with small light reflectors will be put on their head. Prior to the FDOPA administration, a transmission scan will be obtained. Subsequently, approximately 10-12 mCi of FDOPA will be injected as a bolus in an arm vein and a dynamic scan will be obtained, with 22 frame protocol and a total scan duration of 90 min. After the completion of the scan, subjects will empty their bladder and will be instructed to void at 2-hour intervals thereafter.